Practice question

**Flux change example** coil 150 turns area 0.06 m² B 0.14 T drops to zero in 0.3 s, ΔΦ = B A =0.14×0.06=0.0084 Wb per turn, ΔΦ/Δt=0.028 Wb/s, e=150×0.028=4.2 V, illustrating calculation from B and area. ε = -L (Δ I/Δ t) . Δ I = 2 - 5 = -3 A , Δ t = 0.1 s . ε = 0.4 × (-3/0.1) = 0.4 × (-30) = -12 V . Magnitude = 12 V. Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M